How Vestigial Organs Work

Some say that scientists are changing the rules of the game when they play "Vestigial or Not Vestigial." In particular, opponents of evolution, including proponents of creationism or intelligent design, say that there's no such thing as vestigial organs, because a creator wouldn't design something imperfectly or without purpose. At the very least, those who doubt evolution reject the idea that an atrophied organ is evidence of a common ancestor. One common argument is that if we don't know the purpose of a body part yet, it may be due to a lack of anatomical knowledge.

In many cases, organs believed to be vestigial have been shown to serve an important purpose in the body. For example, the coccyx may assist in holding our insides in and supporting nearby organs, even though it can be removed with few ill effects. The appendix has been shown to function as a producer of white blood cells and antibodies. If a person were to come down with a condition like diarrhea or dysentery, the appendix would repopulate the gut with microbes needed to stave off further infection. In developed countries, we have managed to survive without our appendix largely because of the medicines we have available. To truly test the functionality of the appendix, we'd have to study its removal in underdeveloped countries that still face diseases such as dysentery without modern medicine.

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But no one, not even Charles Darwin or Robert Wiedersheim, ever said that a body part had to be completely functionless or useless to be considered vestigial. A structure is considered vestigial because it's not performing the function it was designed to perform, as compared to other creatures with the same part. While the appendix may have taken on the role of a white blood cell factory, it doesn't serve the digestive function it performs in other animals.

With this kind of dispute, it's hard to know what the final score of "Vestigial or Not Vestigial" is. Just like us humans, it's a work in progress. So while we're at this evolutionary half-time, visit the next page for some more interesting articles.

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Other Creatures With Junk in the Trunk

Humans aren't the only creatures that phase out the functionality of certain parts as they evolve -- many vestigial structures exist in plants and animals as well. Here's a brief list of some other vestigial parts:

W­ings in flightless birds such as the ostrich

Eyes in blind, cave-dwelling animals, including the Mexican tetra and some salamanders